The present invention relates to a piston of internal combustion engine, on which a multiple-layer coating is formed.
U.S. Patent Application Publication No. 2008/0060603 corresponding to Japanese Patent Application Publication No. 2008-56750 (hereinafter referred to as, patent document 1) discloses a previously-proposed piston of internal combustion engine for an automobile, as one method of improving an abrasion resistance or a seizing resistance of the piston.
In this technique, a surface of piston base material is coated by a lower-layer coating composite, and a surface of the lower-layer coating composite is coated by an upper-layer coating composite. The lower-layer coating composite includes an epoxy resin and a polyamide-imide resin as binding resins, and a polytetrafluoroethylene and a molybdenum disulfide as solid lubricants. The upper-layer coating composite includes the epoxy resin and the polyamide-imide resin as the binding resins, a boron nitride as the solid lubricant, and a silicon nitride and an alumina as hard particles. That is, a double-layer coating composite is formed in order to attain a superior abrasion resistance and to improve the seizing resistance and an initial fitting property.